Uses An Excessive DOM Size

Overview

A large DOM tree can harm your page performance in multiple ways.

Network efficiency and load performance. If you server ships a large DOM tree, you may be
shipping lots of unnecessary bytes. This can also slow down page load time, because the
browser may be parsing lots of nodes that aren't even displayed above-the-fold.

Runtime performance. As users and scripts interact with your page, the browser must constantly
re-compute the position and styling of nodes. A large DOM tree in combination with complicated
style rules can severely slow down rendering.

Memory performance. If you use general query selectors such as document.querySelectorAll('li')
you may be unknowingly storing references to a very large number of nodes, which can overwhelm
the memory capabilities of your users' devices.

Recommendations

An optimal DOM tree:

Has less than 1500 nodes total.

Has a maximum depth of 32 nodes.

Has no parent node with more than 60 child nodes.

In general, look for ways to create DOM nodes only when needed, and destroy them when no
longer needed.

If your server ships a large DOM tree, try loading your page and manually
noting which nodes are displayed. Perhaps you can remove the undisplayed nodes from the loaded
document, and only create them after a user gesture, such as a scroll or a button click.